JP2006331686A - Fuel cell stack - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell stack having high power generation efficiency and a long life. <P>SOLUTION: Since the fuel cell stack is constituted so that the temperature in the gas atmosphere in an anode in each unit contained in a pair of cell assemblies is made higher than that in a cathode, dew condensation in the anode is hardly formed. As a result, sudden drop in power generation efficiency is prevented, break of the unit cells hardly occurs, and the life is extended. Since purge for preventing the dew condensation in the anode is made unnecessary, waste of fuel gas is suppressed, economic efficiency is enhanced, and image of safety giving to a user is increased. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a fuel cell stack excellent in power generation efficiency.

  A solid polymer electrolyte fuel cell has an anode composed of a fuel gas diffusion layer and a catalyst layer on one side of a solid polymer electrolyte membrane (hereinafter simply referred to as “electrolyte membrane”) made of a polymer ion exchange membrane. A unit fuel cell (hereinafter simply referred to as “unit battery cell”) having a cathode composed of an oxidant gas diffusion layer and a catalyst layer on the other surface is electrically conductive. It is constituted by being sandwiched by a sex separator.

  This solid polymer electrolyte fuel cell uses a gas containing at least hydrogen gas as a fuel gas, uses a gas containing at least oxygen gas such as air as an oxidant gas, and performs oxidation-reduction reaction between hydrogen and oxygen. The generated electromotive force is used to extract DC electric energy.

  Specifically, in a solid polymer electrolyte fuel cell, an electrolyte in which hydrogen gas in a fuel gas supplied to an anode diffuses in a gas diffusion layer and is protonated in a catalyst layer, and the generated protons are appropriately humidified. While moving to the cathode side through the membrane, electrons generated during the movement move to the cathode side through an external circuit.

  The proton that has moved to the cathode side reacts with oxygen gas in the oxidant gas supplied to the cathode in the catalyst layer of the cathode and electrons that have flowed from the anode side to the cathode side via the external circuit, and water is removed. Generate. In a solid polymer electrolyte fuel cell, direct current electric energy is taken out by using an electromotive force generated in the oxidation-reduction reaction in which water is generated from hydrogen and oxygen.

  Here, since the electromotive force of a solid polymer electrolyte fuel cell composed of a unit battery cell and a set of conductive separators is not practical, in general, a solid polymer electrolyte fuel cell is sufficient. In order to obtain a good electromotive force, it is used as a fuel cell stack in which a plurality of sets of unit battery cells and conductive separators are electrically connected and combined.

  As the form of this fuel cell stack, a stacked fuel cell stack in which the cathode side end face and the anode side end face of the unit battery cells are adjacently stacked and connected in series via a conductive separator, or a unit cell There is a form such as a planar fuel cell stack in which the unit battery cells are connected in series or in parallel by wiring or the like after the cells are arranged in a plane.

  By the way, in the solid polymer electrolyte fuel cell, water is generated at the cathode as described above during the power generation process. Therefore, the water vapor partial pressure in the unit battery cell is higher on the cathode side than on the anode side, and moisture (water vapor) moves from the cathode side to the anode side through the electrolyte membrane due to the difference in water vapor partial pressure. To do.

  On the other hand, due to the electroosmosis phenomenon accompanying proton transfer from the anode to the cathode during the power generation process, there is also movement of water (water vapor) from the anode side to the cathode side through the electrolyte membrane. Here, when the amount of moisture transferred from the anode side to the cathode side due to the electroosmosis phenomenon is smaller than the amount of moisture transferred from the cathode side to the anode side caused by the above-mentioned water vapor partial pressure difference, apparently, Moisture moves from the cathode side to the anode side.

  Such movement of moisture from the cathode side to the anode side may cause condensation on the anode. When dew condensation occurs on the anode, water drops cover the catalyst layer of the anode, thereby reducing the reaction area of the catalyst layer. As a result, the power generation efficiency rapidly decreases, and sometimes power generation becomes impossible.

  Further, in a fuel cell stack configured by connecting unit battery cells in series, when the power generation efficiency of one unit battery cell is drastically reduced, the voltage (electrical energy) extracted from the entire fuel cell stack is suddenly reduced. As a result, not only the function as a fuel cell stack becomes insufficient, but also the unit battery cell with reduced power generation efficiency acts as an electrical resistance on the circuit, resulting in damage to the unit battery cell.

  In particular, in the case of a stacked fuel cell stack, the heat distribution is worse at the center than at the end in the stacking direction of the stack, so the temperature distribution is higher at the center than at the end in the stacking direction. Arise. Therefore, in the negative electrode side in the stacked fuel cell stack, that is, several unit battery cells from the anode side end surface of the stacked unit battery cells, the temperature on the anode side is lower than the temperature on the cathode side. Arise.

  Therefore, some unit battery cells on the negative electrode side in the stacked fuel cell stack are likely to reach the saturated water vapor pressure first on the anode side where the temperature is lower than that on the cathode side. As a result, the power generation efficiency rapidly increases due to condensation on the anode. Reduction is likely to occur. In fact, the first and second unit battery cells from the negative electrode side of the stacked fuel cell stack tend to be more easily damaged than other unit battery cells.

  Conventionally, in order to prevent dew condensation on the anode, for example, as described in Japanese Patent Application Laid-Open No. 2000-243417 (Patent Document 1), the fuel gas in the fuel gas flow path (hydrogen supply / exhaust system) is reduced. Often purging to the outside.

  Here, FIG. 7 is a graph showing the output stability of the fuel cell stack when the purge of fuel gas, which is a measure for preventing condensation on the anode, is not performed. The horizontal axis in the graph of FIG. 7 indicates the operation time (unit: time) of the fuel cell stack, and the vertical axis indicates the output voltage (unit: V). As shown in FIG. 7, when the purge of the fuel gas was not performed, the voltage suddenly dropped within 1 hour after the start of operation, and the fuel cell stack was in a power generation disabled state.

  In addition, cordless devices and household fuel cell stacks do not require as much electromotive force as automotive applications, and the fuel gas flow path is closed on the exhaust side from the viewpoint of long-time operation and economy. There is something. In a stacked fuel cell stack in which one side is closed in the flow path of the fuel gas in this way, since the fuel gas containing moisture is not exhausted to the outside, condensation is particularly likely to occur on the anode in the unit battery cell on the negative electrode side. Become.

Even when such a flow path of the fuel gas is closed on the exhaust port side, purging of the fuel gas as described above is performed in order to prevent condensation on the anode. In this case, the fuel gas in the flow path of the fuel gas is purged to the outside by the supply pressure of the fuel gas by releasing the close in the flow path of the fuel gas every predetermined period.
JP 2000-243417 A

  However, when the fuel gas is purged to prevent condensation on the anode, the amount of waste of the fuel gas is inevitably increased, which shortens the operation time and is not economical. It was. In the case of fuel cell stacks for cordless devices where long-time operation is important, shortening the operation time due to waste of fuel gas is one of the most ignorable problems, and it reduces the user's willingness to purchase There was a point. Similarly, even in the case of fuel cell stacks for households where good fuel economy is important, the uneconomical effect due to the waste of fuel gas is one of the most ignorable problems. There was a problem of causing a drop.

  Further, since the fuel gas is a gas containing hydrogen, there is a problem that the safety image of the user is lowered against the purging of such fuel gas. In particular, when the fuel cell stack is a household fuel cell stack, as a result of the decline in the safety image, the willingness to purchase is reduced even though sufficient safety measures are actually taken. There was a problem.

  The present invention has been made in order to solve the above-described problems, and suppresses waste of fuel gas, reduces anxiety given to the user in terms of safety, and has excellent power generation efficiency and long life. The object is to provide a long fuel cell stack.

  In order to achieve this object, a fuel cell stack according to claim 1 includes a polymer electrolyte membrane, an anode adjacent to one surface of the polymer electrolyte membrane, into which fuel gas flows, and the polymer. A battery assembly comprising a plurality of unit battery cells electrically connected to a surface of the electrolyte membrane adjacent to the surface opposite to the anode and into which an oxidant gas flows. The fuel gas and the oxidant gas are supplied to the anode and the cathode of each unit battery cell in the battery assembly to obtain an electromotive force, respectively, and the gas in the anode of the unit battery cell The temperature of the atmosphere is configured to be higher than the temperature of the gas atmosphere in the cathode. Thereby, the water vapor partial pressure in the fuel cell is regulated by the water vapor partial pressure of the cathode, but since the anode temperature is higher than the cathode temperature, the anode does not reach the saturated vapor pressure. Therefore, condensation is less likely to occur on the anode catalyst surface.

  A fuel cell stack according to a second aspect is the fuel cell stack according to the first aspect, wherein two sets of the battery assemblies are arranged such that end faces on the anode side of the respective battery assemblies face each other. is there. Thereby, the end surface on the anode side where condensation easily occurs in each battery assembly can be arranged inside the fuel cell stack. As a result, the temperature distribution in the fuel cell stack constituted by the combination of the two battery assemblies is represented by the temperature of the gas atmosphere in the anode of each unit battery cell constituting each battery assembly being the gas atmosphere in the cathode. It can be maintained above the temperature. Therefore, condensation is less likely to occur on the anode catalyst surface.

  According to a third aspect of the present invention, there is provided the fuel cell stack according to the first or second aspect, further comprising anode-side heating means for heating the anode-side end portion of the battery assembly. As a result, in each unit battery cell in the battery assembly constituting the fuel cell stack, the temperature of the gas atmosphere in the anode can be made higher than the temperature of the gas atmosphere in the cathode, and condensation is unlikely to occur on the catalyst surface of the anode. Become.

  The fuel cell stack according to claim 4 is the fuel cell stack according to any one of claims 1 to 3, wherein a fuel gas supply path that supplies the fuel gas to an anode of the unit battery cell, and a fuel gas supply path thereof And a fuel gas supply path heating means for heating the inflow side to the battery assembly. Thus, since the fuel gas is heated by the fuel gas supply path heating means and then supplied to the anode of each unit battery cell, the temperature of the gas atmosphere in the anode in each unit battery cell can be increased efficiently. Become. As a result, the temperature of the gas atmosphere in the anode can be made higher than the temperature of the gas atmosphere in the cathode, so that condensation is unlikely to occur on the catalyst surface of the anode.

  The fuel cell stack according to claim 5 is the fuel cell stack according to any one of claims 1 to 4, wherein at least two fuels flow into the anode of the unit battery cell from directions facing each other. A gas supply path is provided.

  Generally, in the fuel cell stack, a common flow path for supplying fuel gas to each unit battery cell is provided, and the fuel gas is introduced from this flow path to the anode side flow path of each unit battery cell. The fuel gas supplied to the anode side flow path contributes to power generation through the fuel gas diffusion layer and the catalyst layer of the anode. On the other hand, there is unreacted gas that does not contribute to power generation, and the flow path is formed to be discharged from the anode side flow path to the discharge common passage. However, depending on the operation state, a phenomenon occurs in which unreacted gas concentrates on a specific unit battery cell having a low fuel gas pressure through the discharge common passage. The unreacted gas contains moisture, and when it concentrates on the anode of a specific unit battery cell, it increases the risk of condensation.

  According to the fuel cell stack of the fifth aspect, the fuel gas flows into one anode included in each unit battery cell from at least two fuel gas supply paths in directions facing each other. Therefore, it can suppress that the unreacted gas containing much moisture flows into other unit battery cells, and as a result, it can suppress that the catalyst surface of an anode is covered with dew condensation.

  According to the fuel cell stack of the present invention, since the phenomenon that the catalyst surface of the anode is covered with condensation is less likely to occur, there is an effect that the sudden decrease in power generation efficiency is prevented and the life of the unit battery cell is improved. In addition, the number of purges of the fuel gas and the purge amount can be reduced to prevent dew condensation on the anode, and in some cases it is not necessary at all, so it is economical and it is possible to extend the operation time of the equipment. There is also an effect. In addition, there is an effect that the image of safety that the user has against purging can be improved.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a diagram for explaining a fuel cell stack 1 according to a first embodiment of the present invention. FIG. 1A is a schematic diagram of the fuel cell stack 1 according to the first embodiment of the present invention. FIG. 1B is a graph showing the temperature distribution in the fuel cell stack 1. In FIG. 1B, the vertical axis indicates the temperature, while the horizontal axis indicates the position in the left-right direction on the paper surface in the fuel cell stack 1 shown in FIG.

  As shown in FIG. 1 (a), the fuel cell stack 1 of the first embodiment is a stacked fuel cell stack, and two sets of battery assemblies configured by stacking eight unit battery cells 20 respectively. 2, a negative electrode 50 and a positive electrode 60 that are voltage extraction terminals in the fuel cell stack 1, a hydrogen gas supply path 30 that supplies hydrogen gas as a fuel gas to each of the unit battery cells 20, and the unit battery cell 20. The hydrogen gas exhaust passage 31 that circulates the exhausted fuel gas (exhaust fuel gas), the air supply passage 40 that supplies air as an oxidant gas to each of the unit battery cells 20, and the unit battery cells 20 are exhausted. And an air exhaust passage 41 through which an oxidant gas flows.

  In the fuel cell stack 1, as shown in FIG. 1A, the hydrogen gas exhaust path 31 is closed (closed) at the terminal end 31a, and the hydrogen gas supplied from the hydrogen gas supply path 30 is used without waste. It is configured to be able to. Although the fuel cell stack 1 has other components such as gas packing, these are well-known configurations and are not the gist of the present invention, so illustration and description are omitted.

  In FIG. 1A, some unit battery cells 20 are schematically shown as unit battery cells X inside. The unit battery cell X, that is, the unit battery cell 20 includes an electrolyte membrane 22 having a thickness of about 60 μm or less constituted by an ion exchange membrane (for example, a fluorine-based membrane such as Nafion (registered trademark) manufactured by DuPont), a fuel The anode 21 that is composed of the gas diffusion layer 26 and the catalyst layer 24 and is disposed adjacent to one side of the electrolyte membrane 22, the oxidant gas diffusion layer 27, and the catalyst layer 25, and the other of the electrolyte membranes 22. And a cathode 23 disposed on the surface side. Hydrogen gas 30 a is supplied from the hydrogen gas supply path 30 to the anode 21, and air 40 a is supplied from the air supply path 40 to the cathode 23.

  As described above, the unit battery cell 20 (unit battery cell X) obtains an electromotive force in accordance with the oxidation-reduction reaction between the hydrogen gas supplied to the anode 21 and the oxygen in the air supplied to the cathode 23. is there.

  Here, the electrolyte membrane 22 used in the fuel cell stack 1 of the present invention will be described in detail. In general, in an electrolyte membrane used in a fuel cell, the higher the moisture content of the membrane, the lower the ohmic loss of the membrane and the higher the power generation efficiency. Also, the higher the relative humidity of the ambient atmosphere, the higher the moisture content of the membrane. However, since a large amount of moisture moves from the anode 21 to the cathode 23 due to the electroosmosis phenomenon accompanying power generation, the relative humidity of the anode 21 decreases, and the moisture content near the anode of the electrolyte membrane 22 decreases remarkably. Therefore, in general, there are many systems in which fuel gas is sufficiently humidified outside and supplied to the fuel cell stack.

  However, when the fuel gas (hydrogen gas 30a) is supplied without being sufficiently humidified externally as in the fuel cell stack 1 of the present invention, the moisture generated at the cathode 23 is positively moved to the anode 21. Therefore, it is required to increase the water content near the anode of the electrolyte membrane 22. For this purpose, it is effective to reduce the thickness of the electrolyte membrane as much as possible in order to further accelerate the moisture transfer from the cathode 23 to the anode 21 due to the water vapor partial pressure difference, thereby enabling highly efficient power generation. Become.

  In addition, since the moisture movement due to the water vapor partial pressure difference is fast, the electrolyte membrane 22 does not significantly dry even when power is generated at a higher current density. Therefore, the output per unit volume can be increased, and further miniaturization becomes possible.

  In order to make these effects possible, the thickness of the electrolyte membrane 22 is desirably at least 60 μm or less. Furthermore, since it has been found that a higher effect can be obtained by setting the thickness of the electrolyte membrane 22 to about 15 to 30 μm, the thickness of the electrolyte membrane 22 may be about 15 to 30 μm. More desirable.

  Two sets of battery assemblies 2 constituting the fuel cell stack 1 of this embodiment include a conductive separator (not shown) on the anode 21 side of one unit battery cell 20 (unit battery cell X) in each set. A conductive separator (not shown) on the cathode 23 side of another unit battery cell 20 (unit battery cell X) is laminated adjacent to each other, and eight unit battery cells 20 are connected in series.

  The fuel cell stack 1 of the present embodiment is arranged so that the negative electrode 50 side of the two battery assemblies 2, that is, the anode 21 side of the unit battery cell 20 constituting the battery assembly 2 faces each other. That is, as shown in FIG. 1A, the end surface on the anode 21 side of the rightmost unit battery cell 20 on the negative electrode 50 side in the battery assembly 2 on the left side of the paper and the negative electrode in the battery assembly 2 on the right side of the paper. The left end unit battery cell 20 on the 50th side is disposed so as to face the end surface on the anode 21 side.

  Note that the fuel cell stack 1 of the present embodiment is such that two sets of cell assemblies 2 are connected in parallel as a result of the two sets of cell assemblies 2 being arranged so that the end surfaces on the anode 21 side face each other. The voltage is taken out from the two negative poles 50 and the two positive poles 60.

  The temperature distribution of the stacked fuel cell stack 1 is the highest in the vicinity of the center because of the difference in heat dissipation between the end in the stacking direction (left-right direction on the paper) and the center, and the temperature at the end in the stacking direction. Is the lowest. In the fuel cell stack 1 of the present embodiment as well, as shown in FIG. 1B, the temperature distribution is highest near the negative pole 50 located at the center and decreases toward the two positive poles 60 located at both ends. is doing.

  Therefore, as is clear from FIG. 1B, in all the unit battery cells 20 (unit electron cells X) in the fuel cell stack 1, the temperature of the gas (hydrogen gas 30a) atmosphere in the anode 21 The temperature of the gas (air 40a) atmosphere becomes higher.

  That is, in the fuel cell stack 1 of this embodiment, as a result of the two battery assemblies 2 being arranged so that the end surfaces on the negative electrode 50 side (end surfaces on the anode 21 side) face each other, The temperature of the gas (hydrogen gas 30a) atmosphere in the anode 21 in the battery cell 20 (unit battery cell X) can be made higher than the temperature of the gas (air 40a) atmosphere in the cathode 23.

  By making the temperature of the gas atmosphere in the anode 21 higher than the temperature of the gas atmosphere in the cathode 23, it is possible to prevent the condensation on the anode 21. As a result, it is possible to prevent a sudden decrease in power generation efficiency in the fuel cell stack 1 and to provide stable electric energy. Moreover, since the electrical resistance of the unit battery cell 20 due to the decrease in power generation efficiency is suppressed and damage to the unit battery cell 20 can be prevented, the life of the fuel cell stack 1 can be improved.

  The temperature difference between the temperature of the gas atmosphere of the anode 21 and the temperature of the gas atmosphere of the cathode 23 is preferably 1 ° C. or more, and more preferably 2 ° C. or more because temperature control becomes easier. By setting this temperature difference to at least 1 ° C. or more, the occurrence of condensation on the anode 21 can be effectively prevented.

  The temperature difference between the gas atmosphere temperature of the anode 21 and the gas atmosphere temperature of the cathode 23 is preferably 5 ° C. or less. If the temperature difference between the temperature of the gas atmosphere of the anode 21 and the temperature of the gas atmosphere of the cathode 23 is too high, the electrolyte membrane 22 tends to dry transiently, and the drying of the electrolyte membrane 22 causes the inability to generate power. . Therefore, by setting this temperature difference to 5 ° C. or less, drying of the electrolyte membrane 22 is surely prevented, and as a result, improvement of power generation efficiency and prevention of breakage by preventing condensation of the anode 21 are more effectively realized. Can do it.

  FIG. 2 is a graph showing the output stability when the hydrogen purge is not performed in the fuel cell stack 1 of the first embodiment having the above-described configuration. The horizontal axis in the graph of FIG. 2 indicates the operation time (unit: time) of the fuel cell stack 1, and the vertical axis indicates the output voltage (unit: V).

  As shown in FIG. 2, the fuel cell stack 1 of the first embodiment falls into a state where power generation efficiency is suddenly lowered or power generation is disabled for at least 24 hours in both low load operation and high load operation. It never happened.

  As described above, the fuel cell stack 1 of the present embodiment is configured by disposing the end faces on the anode 21 side of the two sets of battery assemblies so as to face each other. The end surface on the anode 21 side where condensation easily occurs can be disposed so as to face the inside of the fuel cell stack 1.

  As a result, the temperature distribution in the fuel cell stack 1 constituted by the combination of the two battery assemblies 2 is represented by the temperature of the hydrogen gas 30 a in the anode 21 of each unit battery cell 20 constituting each battery assembly 2. (The temperature of the gas atmosphere) can be made higher than the temperature of the air 40a in the cathode 23 (the temperature of the gas atmosphere).

  Therefore, the dew condensation generated on the anode 21 can be prevented, the sudden decrease in power generation efficiency can be prevented, the unit battery cell 20 is hardly damaged, and the life can be improved. Further, as is clear from FIG. 2, the number of purges and the purge amount of the fuel gas conventionally performed for preventing the condensation of the anode 21 can be reduced. In some cases, it is not necessary at all. The waste of 30a is suppressed and not only economical, but also the image of safety held by the user can be improved.

  Next, a second embodiment of the present invention will be described with reference to FIG. FIG. 3A is a schematic diagram of the fuel cell stack 1 in the second embodiment of the present invention.

  The fuel cell stack 1 according to the first embodiment described above is configured such that the end faces on the anode 21 side of the two battery assemblies 2 are arranged to face each other, so that the inside of the anode 21 of each unit battery cell 20 is provided. The temperature of the gas atmosphere was made higher than the temperature of the gas atmosphere in the cathode 23.

  As shown in FIG. 3A, the fuel cell stack 1 according to the second embodiment is mainly composed of a set of battery assemblies 2 and a negative electrode 50 and a positive electrode 60 that are voltage extraction terminals. Is. In the description of the fuel cell stack 1 of the second embodiment, the same parts as those of the fuel cell stack 1 of the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.

  As shown in FIG. 3A, the negative electrode 50 in the fuel cell stack 1 of the second embodiment has a heater 70 for heating the end portion on the anode 21 side in the battery assembly 2 on the negative electrode 50 side. Is provided. Although various types of heaters can be used as the heater 70, a thin and inexpensive heater such as a film heater (for example, a silicon heater) is preferable from the viewpoint of miniaturization of the fuel cell stack 1 and manufacturing cost.

  FIG. 3B is a graph showing the temperature distribution in the fuel cell stack 1 of the second embodiment. In FIG. 3B, the vertical axis indicates the temperature, while the horizontal axis indicates the position in the horizontal direction of the paper in the fuel cell stack 1 of the second embodiment shown in FIG. 3A.

  The solid line in FIG. 3B shows the temperature distribution of the fuel cell stack 1 in the present embodiment. For comparison, the temperature distribution on the negative electrode 50 side in a conventional fuel cell stack in which the heater 70 is not provided. Is indicated by a dotted line.

  As apparent from FIG. 3B, by attaching the heater 70 to the negative electrode 50, the temperature distribution on the negative side 50, which is lower than the temperature in the vicinity of the center in the conventional fuel cell stack and causes condensation on the anode, is clear. However, in each unit battery cell 20, the temperature of the hydrogen gas 30a in the anode 21 (temperature of the gas atmosphere) was higher than the temperature of the air 40a in the cathode 23 (temperature of the gas atmosphere).

  Therefore, according to the fuel cell stack 1 of the second embodiment, by providing the heater 70 on the negative electrode 50 side, the end on the anode 21 side of each unit battery cell 20 constituting the battery assembly 2 in the fuel cell stack 1 is provided. The portion can be heated so that the temperature of the gas atmosphere in the anode 21 is higher than the temperature of the gas atmosphere in the cathode 23.

  Therefore, the dew condensation generated on the anode 21 can be prevented, the sudden decrease in power generation efficiency can be prevented, the unit battery cell 20 is hardly damaged, and the life can be improved. As a result, it is possible to reduce the number of purges and the purge amount of the fuel gas that has been conventionally performed to prevent dew condensation on the anode 21, and in some cases it is not necessary at all, so that waste of the hydrogen gas 30 a as the fuel gas is suppressed. In addition to being economical, it is possible to improve the safety image of the user.

  Next, a third embodiment of the present invention will be described with reference to FIG. FIG. 4 is a schematic diagram of the fuel cell stack 1 in the third embodiment of the present invention. In the description of the fuel cell stack 1 of the third embodiment, the same parts as those of the fuel cell stack 1 of the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.

  In the fuel cell stack 1 of the second embodiment described above, the heater 70 for heating the negative electrode 50 side is provided, so that the temperature of the gas atmosphere in the anode 21 of the unit battery cell 20 is changed to the gas atmosphere in the cathode 23. It was made to become higher than the temperature of. In the fuel cell stack 1 of the third embodiment, as shown in FIG. 4, a heater 80 is provided on the inflow side to the battery assembly 2 in the hydrogen gas supply path 30 instead of the heater 70.

  As a result of providing the heater 80 on the inflow side to the battery assembly 2 in the hydrogen gas supply path 30, the hydrogen gas 30a heated by the heater 80 flows into each anode 21 and effectively raises the temperature of each anode 21. be able to.

  Thus, the fuel cell stack 1 of the third embodiment in which the heater 80 is installed exhibits a temperature distribution similar to that shown in FIG. That is, the temperature of the gas atmosphere in the anode 21 of each unit battery cell 20 constituting the battery assembly 2 in the fuel cell stack 1 can be made higher than the temperature of the gas atmosphere in the cathode 23.

  Therefore, the fuel cell stack 1 of the third embodiment can also prevent dew condensation generated at the anode 21, prevent a sudden decrease in power generation efficiency, and prevent the unit battery cell 20 from being damaged, thereby improving the life. Can be made. As a result, it is possible to reduce the number of purges and the purge amount of the fuel gas that has been conventionally performed to prevent dew condensation on the anode 21, and in some cases it is not necessary at all, so that waste of the hydrogen gas 30 a as the fuel gas is suppressed. In addition to being economical, it is possible to improve the safety image of the user.

  Although various types of heaters can be used as the heater 80, a flexible heater such as a film heater (for example, a silicon heater) that can be mounted so as to surround the hydrogen gas supply path 30 is preferable. Since the heater 80 is mounted so as to surround the periphery of the hydrogen gas supply path 30, the hydrogen gas 30 a can be heated uniformly, so that the temperature of the gas atmosphere in the anode 21 is adjusted to the temperature of the gas atmosphere in the cathode 23. It can surely be higher than the temperature.

  Next, a fourth embodiment of the present invention will be described with reference to FIG. FIG. 5 is a schematic view of the fuel cell stack 1 in the fourth embodiment of the present invention. In the description of the fuel cell stack 1 of the fourth embodiment, the same parts as those of the fuel cell stack 1 of the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.

  The fuel cell stack 1 according to the first embodiment described above is configured such that the hydrogen gas 30a is supplied from the single hydrogen gas supply path 30 to the anode 21 of each unit battery cell 20. The fourth embodiment Then, the second hydrogen gas supply path 90 of another system for flowing in the hydrogen gas 90a from the direction opposite to the inflow direction of the hydrogen gas 30a in the first hydrogen gas supply path 30 is further provided. Hydrogen gas 30 a and 90 a are supplied from the supply paths 30 and 90 to the anode 21.

  The second hydrogen gas supply path 90 is provided with an opening / closing valve 110 that supplies or shuts off the hydrogen gas 90 that is fuel. Further, an exhaust path 91 is provided on the side of the fuel cell stack 1 with respect to the opening / closing valve 110, branching from the fuel gas supply path 90 and via the opening / closing valve 111.

  During normal operation, the opening / closing valve 110 of the second hydrogen gas supply path 90 is opened and the exhaust opening / closing valve 111 is closed. Moreover, the gas pressures of the hydrogen gas 30a in the hydrogen gas supply path 30 and the hydrogen gas 90a in the hydrogen gas supply path 90 are equal, and these hydrogen gases 30a and 90a face the anode 21 of each unit battery cell 20, respectively. Supplied from the inflow direction. The flow of the hydrogen gas 30a, 90a is a flow that flows from the hydrogen gas supply path 30, 90, which is a common flow path, toward the anode, and the unreacted gas containing a large amount of moisture near the anode 21 is a common flow path. Thus, it is possible to prevent concentration on other specific unit battery cells 20.

  Further, in a state where the hydrogen gas 30a is supplied from the first hydrogen gas supply path 30, the first hydrogen gas supply path 90 is closed by closing the opening / closing valve 110 and further opening the exhaust opening / closing valve 111. By the inflow of the hydrogen gas 30 a from the hydrogen gas supply path 30, the hydrogen gas containing moisture and impurities in the unit battery cell 20 can be discharged (purged) out of the fuel cell stack 1.

  Next, a fifth embodiment of the present invention will be described with reference to FIG. FIG. 6 is a schematic view of a fuel stack 100 that is a fuel cell stack according to a fifth embodiment of the present invention. In the description of the fuel cell stack 100 of the fifth embodiment, the same parts as those of the fuel cell stack 1 of the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.

  In the first to fourth embodiments described above, the stacked fuel cell stack 1 has been described. In the fifth embodiment, a planar fuel cell stack 100 in which the unit battery cells 20 are arranged on a plane will be described.

  As shown in FIG. 6, the fuel cell stack 100 of the fifth embodiment includes two battery assemblies 2 each including three unit battery cells 20 arranged on a plane, and unit battery cells 20. A hydrogen gas supply path 30 for supplying hydrogen gas as a fuel gas to each unit and an air supply path 40 for supplying air as an oxidant gas to each of the unit battery cells 20 are provided.

  In FIG. 6, the detailed configuration is omitted in order to prevent the drawing from becoming complicated. However, in the fuel cell stack 100 of the fifth embodiment, the hydrogen gas 30a supplied from the hydrogen gas supply path 30 is not exhausted to the outside. As described above, the flow path of the hydrogen gas 30a is closed at the end (not shown), and the supplied hydrogen gas 30a can be used without waste.

  In the battery assembly 2, the unit battery cells 20 are connected in series by a wiring (not shown). The electromotive force obtained by the oxidation-reduction reaction generated by the hydrogen gas 30a and the air 40a supplied to the unit battery cells 20 from the hydrogen gas supply path 30 and the air supply path 40, respectively, is a positive electrode (not shown) and It is taken out from a negative pole and a positive pole (both not shown) which are voltage take-out terminals in the fuel cell stack 100 taken out from the negative pole.

  As shown in FIG. 6, the two battery assemblies 2 are arranged so that the anodes 21 face each other. Therefore, since the heat dissipation in the fuel cell stack 100 is poor and the anode 21 side of each unit battery cell 20 is arranged at the center side in the vertical direction of the drawing where the temperature is highest, the gas in the anode 21 in all the unit battery cells 20 is disposed. The temperature of the (hydrogen gas 30a) atmosphere can be made higher than the temperature of the gas (air 40a) atmosphere in the cathode 23.

  Therefore, the dew condensation generated on the anode 21 can be prevented, the sudden decrease in power generation efficiency can be prevented, the unit battery cell 20 is hardly damaged, and the life can be improved. As a result, it is possible to reduce the number of purges and the purge amount of the fuel gas that has been conventionally performed to prevent dew condensation on the anode 21, and in some cases it is not necessary at all, so that waste of the hydrogen gas 30 a as the fuel gas is suppressed. In addition to being economical, it is possible to improve the safety image of the user.

  The present invention has been described above based on the embodiments. However, the present invention is not limited to the above-described embodiments, and various modifications and changes can be easily made without departing from the spirit of the present invention. Can be inferred.

  For example, in the above embodiment, the fuel cell stack in which the end (end 31a) of the flow path of the hydrogen gas 30a, 90a is closed so that the hydrogen gas 30a, 90a supplied to each unit battery cell 20 is not exhausted to the outside. Although described with reference to 1,100, a fuel cell stack having a configuration in which the hydrogen gas 30a is exhausted to the outside may be used.

  In addition, as a result of the fuel cell stack 1 of the first embodiment being disposed on the end surface facing the anode 21 facing each other in the two battery assemblies 2, the two battery assemblies 2 are connected in parallel. In the above description, the voltage is taken out from one negative electrode 50 and two positive electrodes 60. However, two negative electrodes are independently provided from the end surfaces of the two battery assemblies 2 on the anode 21 side. The poles may be provided adjacent to each other in a state of being insulated from each other, and may be configured to be connected in series with the two positive poles 60 to extract the voltage.

  Further, in the fuel cell stack 1 of the fourth embodiment, by providing the two systems of hydrogen gas supply paths 30 and 90, the hydrogen gas 30a and 90a flowing into the one anode 21 from the two paths in the opposite direction is provided. It was configured to supply. This does not mean that two hydrogen gas storage bodies are required for the fuel. For example, two hydrogen gas supply paths 30 and 90 are branched from one hydrogen gas storage body. You may comprise.

  In addition, the present invention is achieved by making the temperature of the gas atmosphere in the anode 21 in each unit battery cell 20 higher than the temperature of the gas atmosphere in the cathode 23, so that the hydrogen gas 30a exemplified in the above embodiment and The air 40a is not limited to these, and it can be easily guessed that various gases conventionally used as fuel gas and oxidant gas can be used.

(A) is a schematic diagram of the fuel cell stack in the first embodiment of the present invention, and (b) is a graph showing the temperature distribution in the fuel cell stack of the first embodiment. 4 is a graph showing output stability when hydrogen purge is not performed in the fuel cell stack of the first embodiment. (A) is a schematic diagram of the fuel cell stack in the second embodiment of the present invention, and (b) is a graph showing the temperature distribution in the fuel cell stack of the second embodiment. It is a schematic diagram of the fuel cell stack in 3rd Example of this invention. It is a schematic diagram of the fuel cell stack in 4th Example of this invention. It is a schematic diagram of the fuel cell stack in 5th Example of this invention. It is a graph which shows the output stability of a fuel cell stack when not purging the fuel gas which is a dew condensation prevention measure of an anode.

Explanation of symbols

1,100 Fuel cell stack 2 Battery assembly 20 Unit battery cell 21 Anode 22 Electrolyte membrane (polymer electrolyte membrane)
23 Cathode 30,90 Hydrogen gas supply path (fuel gas supply path)
30a, 90a Hydrogen gas (fuel gas)
40a Air (oxidant gas)
70 Heater (Anode side heating means)
80 Heater (fuel gas supply path heating means)

Claims (5)

A polymer electrolyte membrane, an anode adjacent to one side of the polymer electrolyte membrane, into which fuel gas flows, and an inner side adjacent to the surface of the polymer electrolyte membrane opposite to the anode A plurality of unit battery cells composed of a cathode into which an oxidant gas is introduced are electrically connected to form a battery assembly, and the anode and cathode of each unit battery cell in the battery assembly are connected to each other. In the fuel cell stack for obtaining an electromotive force by supplying the fuel gas and the oxidant gas,
The fuel cell assembly, wherein the temperature of the gas atmosphere in the anode of the unit battery cell is higher than the temperature of the gas atmosphere in the cathode.   2. The fuel cell stack according to claim 1, wherein two sets of the battery assemblies are arranged so that end faces on the anode side of the respective battery assemblies face each other.   3. The fuel cell stack according to claim 1, further comprising an anode-side heating unit that heats an anode-side end portion of the battery assembly. 4. A fuel gas supply path for supplying the fuel gas to the anode of the unit battery cell;
The fuel cell stack according to any one of claims 1 to 3, further comprising a fuel gas supply path heating means for heating an inflow side to the battery assembly in the fuel gas supply path. 5. The fuel cell according to claim 1, further comprising at least two fuel gas supply paths through which the fuel gas flows from opposite directions to the anode of the unit battery cell. stack.

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